The number of electronic devices continues to increase. Furthermore, electronic devices are becoming more mobile, and at the same time, more powerful. Thus, many transistors are being packaged into devices for communication, general computing, consumer electronics, and other areas. A flip chip device is an electronic chip that is installed on a circuit board, with connections between the chip and the circuit board formed by solder bumps rather than wires. Flip chip devices are playing an important role in the realization of products for these areas. Thus, more than ever before, reliability and durability in electronics fabrication is important.
A significant issue in modern flip chip packaging is the tight interconnection via an array of solder joints of two structures made of widely different materials: the silicon integrated circuit device, and the organic laminate substrate. The solder joints must be protected from fatigue damage resulting from different thermal strains in the device and substrate, using a stiff underfill material. The underfill tightly couples the device to the substrate, therefore reducing the strain on the solder joints, but at the cost of creating significant problems elsewhere. These problems include package warpage, strain on the thermal interface layer, underfill adhesion and cracking in thermal cycling, among others. Thus, as a chip is powered on and off many times over its lifetime, the thermal cycling can cause problems that can impact reliability. Therefore, it is desirable to have improvements in flip chip devices.